The present invention relates to a plating method, and a semiconductor fabrication method and a circuit board fabrication method using the plating method, more specifically, a plating method which can realize high reliability, and a semiconductor device fabrication method and a circuit board fabrication method using the plating method.
In the multi-layer interconnections formed on semiconductor substrates or circuit boards, inter-layer insulation films are required for the electric insulation between the interconnection layers.
In the steps of forming such inter-layer insulation films, recently the technique of forming an inter-layer insulation film by applying a sheet of a resin (hereinafter called a resin sheet) to a semiconductor substrate or a circuit board by vacuum press is noted. Forming an inter-layer insulation film of the resin sheet can much reduce the material waste in comparison with forming an inter-layer insulation film by spin coating, and resultantly inter-layer insulation films can be formed at lower costs.
In forming an interconnection on a resin layer formed by using such resin sheet, the interconnection can be formed by, e.g., the following technique.
First, contact holes are formed in the resin layer by a laser or others. Next, desmearing treatment is performed. The desmearing treatment is a chemical treatment for removing smears of the resin produced when the contact holes are formed in the resin layer by the laser or others. The desmearing treatment removes the smears out of the contact holes and forms convexities and concavities in the surface of the resin layer. In the desmearing treatment, the resin layer is immersed in, e.g., an alkaline solution of permanganic acid of 50-90° C. for about several minutes to several tens minutes. Then, a seed layer for forming a plating film is formed by electroless plating on the resin layer with the concavities and convexities formed in the surface by the desmearing treatment. The seed layer is formed, anchored in the concavities, i.e., a number of fine pores, formed in the surface of the resin layer, whereby the adhesion between the resin layer and the plating film is sufficiently secured. This phenomena is called anchor effect. Then, a photoresist film is formed on the entire surface of the resin layer, and openings are formed in the photoresist film by photolithography. Next, a plating film is formed on the seed layer in the openings by electroplating. Because of the sufficient adhesion between the seed layer and the resin layer, the plating film is secured to the resin layer via the seed layer. Finally, the photoresist film is released, and the interconnection is formed on the resin layer.
Patent Reference 1 discloses a method for forming a plating film on a resin substrate, in which a resin substrate layer with UV radiation applied to is immersed in an alkaline solution to subject the resin substrate to the desmearing treatment, whereby the adhesion between the resin substrate and the plating film is retained firmly.
Patent Reference 2 discloses a method for forming conductor circuit pattern on a molding formed by injection molding, in which when a resist applied to the surface of the injection molding, laser beams are applied also to the surface of the injection molding to thereby roughen the surface of the injection molding, whereby the step of roughening the surface of the injection molding can be omitted.
[Patent Reference 1]
Specification of Japanese Patent Application Unexamined Publication No. 2003-27250
[Patent Reference 2]
Specification of Japanese Patent Application Unexamined Publication No. Hei 11-6073
As disclosed in Patent Reference 1, when an object (the resin substrate) for the plating film to be formed on is immersed in an alkaline solution to thereby make the desmearing treatment, deep pores of several μm to ten-odd μm are formed in the surface of the resin layer, which makes it difficult to form a micronized interconnection pattern on the surface of the resin substrate by using a photoresist film. When the pitch of the interconnections formed on the resin substrate is small, the possibility that short circuits, etc. may take place is higher.
As disclosed in Patent Reference 2, when the surface of an object (the resin substrate) for the plating film to be formed on is roughened by applying laser beams, the application of laser beams takes a long time when the surface for the plating film to be formed on is large.